Generation of zonal flow and magnetic field in the ionospheric E-layer

Abstract

We review the generation of zonal flow and magnetic field by coupled electromagnetic ultra-low-frequency waves in the Earth’s ionospheric E-layer. It is shown that, under typical ionospheric E-layer conditions, different planetary low-frequency waves can couple with each other. Propagation of coupled internal-gravity–Alfvén, coupled Rossby–Khantadze and coupled Rossby–Alfvén–Khantadze waves is revealed and studied. A set of appropriate equations describing the nonlinear interaction of such waves with sheared zonal flow is derived. The conclusion on the instability of short-wavelength turbulence of such coupled waves with respect to the excitation of low-frequency and large-scale perturbation of the sheared zonal flow and sheared magnetic field is deduced. The nonlinear mechanism of the instability is based on the parametric triple interaction of finite-amplitude coupled waves leading to the inverse energy cascade towards longer wavelength. The possibility of generation of an intense mean magnetic field is shown. Obtained growth rates are discussed for each case of the considered coupled waves.

Generation of Zonal Flow and Magnetic Field by Planetary Waves in the Earth’s Ionosphere

“…Nonlinear dynamics of CRAK EM planetary modes in the ionospheric E-layer is investigated (see details in [16] [30]). It is shown that under the prevalent action of Hall conductivity, owing to the latitudinal non-homogeneity of both the Coriolis parameter and stationary geomagnetic field, a new type of CRAK wave can propagate.…”

“…But during the last decade a great amount of publications revealed different nonlinear mechanisms leading to the generation of sheared zonal flow. Namely the excitation of zonal flow based on the triple planetary waves nonlinear parametric instability in the Earth's ionospheric medium was widely investigated (see [14] [16]- [30] and references cited in).…”

“…basic 2D nonlinear equations describing the dynamics of zonal flow generation and coupled internal-gravity and Alfven wave propagation under the Boussinesq approximation are constructed (see details in[14] [22] [28][30]). Caused by the gravity force action altitude distribution of the equilibrium density and pressure of the medium (so called stratification) is taken into account.…”

“…It is shown that in the Earth's E-layer under the prevalent Hall conductivity due to the latitudinal non-homogeneity of geomagnetic field, slow and fast waves can couple and form EM CRK waves (see details in[12] [13] [26] [27] [29][30]). A linear dispersion relation for the CRK waves is obtained.…”

Brief Communication: A modified Korteweg–de Vries equation for Rossby–Khantadze waves in a sheared zonal flow of the ionospheric E layer

“…Jian et al (2009) investigated non-linear propagation of Rossby waves in stratified neutral fluids with zonal shear flow and obtained a modified Korteweg-de Vries (mKdV) equation with cubic non-linearity. Generation of the zonal flow along with the magnetic field in the ionospheric E plasma by Rossby-Khantadze EM planetary waves was also discussed (Kaladze et al, 2012;Kahlon and Kaladze, 2015). The possibility of a magnetic field generation of 10 3 nT is predicted.…”